The present invention relates to emergency lighting systems, and more particularly to an emergency lighting unit having a remote test feature and improved circuitry for prolonging battery life.
Emergency lighting units have come into wide use for providing energency lighting to commercial and residential buildings in the event of AC line failure Typically, such units are mounted high on the wall of a hall or stairway, and are connected to the AC line supplying lighting in that hall or stairway so as to provide lighting to the area upon loss of power. Examples of such units in commercial use are shown in the model TC6L lead acid battery and model TC6N and A6N nickel cadmium emergency lighting units manufactured by Teledyne Big Beam of Crystal Lake, Ill. Such units are available with a variety of different lighting heads to accommodate different lighting requirements, as well as with a variety of different battery voltages and capacities to accommodate different lighting requirements.
To be certain that emergency lighting units are providing the desired degree of protection it is desirable that they be periodically tested, and in many installations such tests are established as a regular procedure. Unfortunately, to test prior emergency lighting units it was necessary for the user to individually actuate a test button on each unit housing to momentarily interrupt the AC line, and then observe after a short time delay the illumination of the unit flood lights. Since the housings of such units were often located in high relatively inaccessible locations, testing was often been an arduous, time-consuming task, particularly where a large number of emergency lighting units had to be tested.
Accordingly, the need has existed for an emergency lighting unit which can be quickly and economically tested, without the need to gain access to the unit housing. The present invention satisfies this requirement through the provision of a radio frequency test link, actuated by a small hand-held battery-operated radio transmitter.
A further requirement of emergency lighting units is that the unit provide a long shelf life prior to actual use, and a long period of illumination when called into use. The present invention meets this requirement through the provision of a variable-rate battery charging circuit which maintains the battery in an optimum state of charge, and a low-voltage cut-out circuit which prevents excessive discharge of the battery when the lighting unit is called into use.